what is involved in putting one?

[imported_admin]

strobhen's information is incorrect...

There are two branches of superchargers: fixed-displacement and non-fixed displacement. Fixed-displacement (Roots, twin-screw) pump a specific volume of air per revolution and do not permit reverse flow. Air comes in the inlet port and then the port closes. The air is moved to the outlet port, that port opens, and the air discharges. At no time, and regardless of pressure, can air go backward through the supercharger.

Non-fixed displacement superchargers (centrifugal) push an unspecified amount of air along, much like a fan blade, so air can flow backward if conditions warrant. Nothing closes to block the flow. Only air being pushed by blades, much like a propeller, influences it to travel toward the engine. If boost at the compressor outlet suddenly gets too high, as when the throttle (downstream of the supercharger) is slammed shut at high supercharger impeller speed, the air can reverse directions and go right back out through the compressor, just as air could flow backward through a propeller if a great enough force were pushing it.

<blockquote>quote:</font><hr>Originally posted by strobhen:
The impeller doesn't compress air, it just moves a lot of it.<hr></blockquote>

Centrifugal and twin-screw superchargers have internal compression ratios, Roots do not. A supercharger with an internal compression ratio is one in which both volume and pressure vary as the air passes through. As the bit of air passes through, it is continuously forced into a smaller volume, which also increases the pressure. Upon reaching the discharge port, it's already compressed.

Of course superchargers compress air... they're called "compressors" for a reason.

Even Roots "blowers" compress air, only in their case the compression occurs after the air is discharged into the intake manifold.

<blockquote>quote:</font><hr>Originally posted by strobhen:
There are two kinds of superchargers. There is the "Roots" supercharger. It is a twin screw design that makes a lot of boost down low, and is mainly used on carburated & OEM applications. They are torque monsters and spin up very quickly. The other kind is called a Centrifugal Supercharger, which is basically a belt driven turbo. It is more efficient than the roots, less than the turbo, but also has less lag than the turbo and is a tad cheaper.<hr></blockquote>

There are three types as described above, and they fall into two categories. Each has it's own unique advantages and disadvantages. On F-Body applications centrifugal is by far the most common because of simplicity of installation and price. Twin-screw is superior but the engine must be designed with the supercharger in mind--a screw supercharger is hardly a direct bolt-on.

<blockquote>quote:</font><hr>Originally posted by Arctc Wolf:
when installing a sc kit, the kit will give you instructions as to how and when to put a part on, as well as give you all the components you'll need.<hr></blockquote>

Good advice for the original question. Key word being "kit"!

<blockquote>quote:</font><hr>Originally posted by strobhen:
No, a supercharger does not compress air and then spit compressed air into the engine. It is a very powerful fan that spits a lot of uncompressed air into an engine -- the only reason air in the engine becomes compressed is because it cannot move the air out fast enough.<hr></blockquote>

In a centrifugal supercharger, the air is compressed before it even leaves the discharge port of the supercharger. A supercharger does NOT simply push "uncompressed" air. You know the snail-like outer housing of a centrifugal? The cross-sectional volume of that snail path is ever-decreasing, thus the pressure is ever-increasing until it reaches the discharge port.

<blockquote>quote:</font><hr>Originally posted by strobhen:
There is nothing in the mechanism to compress the air. Air is compressed in the engine because you have an engine that puts out, say, 500 cfm of air and a supercharger that pumps in 1000 cfm of air. Where does that other 500 cubic feet of air per minute go? Nowhere, so the incoming air must compress it to make room inside a static container. Very little if any compression takes place in a supercharger.<hr></blockquote>

That right there is just plain wrong. There IS something in the supercharger to compress the air--it's entire design! They're called compressors for a reason! If you don't believe me, pick up a book about it and READ! Don't sit here spewing out incorrect information. As I said at the top of my post, you are thinking too much and confusing yourself. The gist of what you're saying is correct but your logic with regards to compression are incorrect.

<blockquote>quote:</font><hr>Originally posted by daWhoady:
I guess I was mistaken. strobhen, you explained it beautifully.<hr></blockquote>

No, strobhen is confusing himself and others.

[ July 07, 2002: Message edited by: Stefan ]</p>

[imported_admin]

Furthermore...

If a supercharger was just a big fan that pumped uncompressed air into the engine, why wouldn't it just be a linear section of pipe with a fan in it? Superchargers alter the direction of the air passing through. Air comes in the inlet port (the big hole) and then the impeller moves it around the snail-like outer housing to the outlet port. If you were to stick a boost gauge right at the outlet port you would see boost there even if the supercharger was just spinning while not connected to anything at all--i.e. you had it disconnected in your garage and just happened to spin the impeller fast enough to generate boost. The compression does NOT depend on the container the air is being forced into.

To clarify: Something that would just move uncompressed air would be a propeller blade stuck in a 3" diameter section of intake pipe. A supercharger is by it's very nature an air compressor and is fundamentally far different--it DOES compress air.

As an illustration, here is a pic of my ATI P600B showing the difference in diameter between the inlet and outlet ports. I took this picture 2 days ago (thanks Jenn for the polish!).

www.projectvirus.com/albums/prochargerrepair/images/polished100.jpg

[ July 07, 2002: Message edited by: Stefan ]</p>

[strobhen]

<blockquote>quote:</font><hr>strobhen's information is incorrect...<hr></blockquote>

Afraid not [img]smile.gif[/img]

<blockquote>quote:</font><hr>There are two branches of superchargers: fixed-displacement and non-fixed displacement. Fixed-displacement (Roots, twin-screw) pump a specific volume of air per revolution and do not permit reverse flow. Air comes in the inlet port and then the port closes. The air is moved to the outlet port, that port opens, and the air discharges. At no time, and regardless of pressure, can air go backward through the supercharger.<hr></blockquote>

Sounds good to me, I do not know a damn thing about roots or screw type except they make boost down low. I'll conceded any points you want to make about those types of superchargers.

<blockquote>quote:</font><hr>Non-fixed displacement superchargers (centrifugal) push an unspecified amount of air along, much like a fan blade, so air can flow backward if conditions warrant. Nothing closes to block the flow. Only air being pushed by blades, much like a propeller, influences it to travel toward the engine. If boost at the compressor outlet suddenly gets too high, as when the throttle (downstream of the supercharger) is slammed shut at high supercharger impeller speed, the air can reverse directions and go right back out through the compressor, just as air could flow backward through a propeller if a great enough force were pushing it.<hr></blockquote>

Again, this is true, but you will soon find out that a propeller and centrifugal fan are two completely different things. I want to make it very clear that anything I say from here on out applies only to centrifugal superchargers.

<blockquote>quote:</font><hr>In a centrifugal supercharger, the air is compressed before it even leaves the discharge port of the supercharger. A supercharger does NOT simply push "uncompressed" air. You know the snail-like outer housing of a centrifugal? The cross-sectional volume of that snail path is ever-decreasing, thus the pressure is ever-increasing until it reaches the discharge port.<hr></blockquote>

Ok, first, this is how a centrifugal fan of any kind works.

Air is sucked into the middle of the fan, and is then slung to the outer housing, and then forced out the opening, that snail type opening is common to all centrifugal fans, and in itself provides absolutely no compression (assuming the opening is big enough to let out the air the fan pumps in).

Your A/C fan does not try to compress air, and your water pumps do not try to compress water (most water pumps are centrifugal).

So the only thing left to compress the air is the smaller volume of the outlet diameter.

Oh, and I would like to thank you for posting the image of the supercharger, helps me make a point.

First off, the cross sectional path in that snail housing is ever-increasing. That supercharger spins counterclockwise. Air is slung to the outside of the housing, spun counterclockwise until forced out of the opening.

At any given point in the path of the outer housing, it needs to hold all the air slung to that point and all the air before it. So its very small at the "beginning" of the path (where it is smallest), and gets larger & larger to handle the larger volume of air as you go around, until the air is finally forced out.

I don't mean to be rude, but perhaps you need to read up on your supercharger more.

How am I so certain that it spins counterclockwise? Look at the path, if it spun clockwise you would be dumping air from a pin-sized hole into a 3" pipe, and the air would be going the wrong way. If its spinning clockwise, the engineer needs to be shot. Plus, the very compressed air from that pinhole would be shot into a much larger container and lose much of its compression -- it doesn't make sense to do that.

This is actually very interesting, because by that design, the supercharger is minimizing pressure and maximizing air flow. I'm going to stick by my opinion that the sheer amount of air coming out of the supercharger is much more important in creating boost than any compression that takes place inside the supercharger.

But wait! The 3" outlet is still smaller than the 3.75" inlet. Don't worry, I haven't forgotten. That's next.

<blockquote>quote:</font><hr>If a supercharger was just a big fan that pumped uncompressed air into the engine, why wouldn't it just be a linear section of pipe with a fan in it? Superchargers alter the direction of the air passing through. Air comes in the inlet port (the big hole) and then the impeller moves it around the snail-like outer housing to the outlet port. If you were to stick a boost gauge right at the outlet port you would see boost there even if the supercharger was just spinning while not connected to anything at all--i.e. you had it disconnected in your garage and just happened to spin the impeller fast enough to generate boost. The compression does NOT depend on the container the air is being forced into.

To clarify: Something that would just move uncompressed air would be a propeller blade stuck in a 3" diameter section of intake pipe. A supercharger is by it's very nature an air compressor and is fundamentally far different--it DOES compress air.<hr></blockquote>

I said before you would find out a propeller and centrifugal fans are two very different things.

A propeller, or axial fan, can move a lot of air. But it cannot handle backpressure -- which is a big problem when you are trying to compress air. Those kinds of fans are used in open systems, where pressure is not an issue. Centrifugal fans handle backpressure very well, and are one of the best choices in creating pressure.

If you put a boost gauge at the mouth of that supercharger, it will read 0 boost. Why? Because all the air is going out of that supercharger is almost instantly dispersing into the atmosphere. If you put inside the supercharger, it might read some boost. But that air is going to be hauling *** (for lack of a better term) out of that opening.

And it is absolutely incorrect for you to say that PSI does not depend on the container of the air. Ideal gas law, PV=nRT. P is pressure, V is volume, n is the number of molecules of air in moles, R is a constant, and T is Temperature. This is an irrefutable law, PSI is very dependant on the container. Remember also that in any container, there can be only one pressure (overall, its possible for there to be a higher pressure for the fractions of a second it takes the air to disperse through the container).

Is the air coming out of the supercharger slightly compressed? Yes, it is. Is it compressed at 30 psi? Hah, no.

It is the sheer volume of air entering the engine that will create the boost we see, not boost created inside the supercharger. If you still don't believe me, I will prove it through math -- I just don't want to take the time to do that if I don't have to. I don't need to pick up some book because I've been through the classes already.

Let me make a couple points clear, that I feel are the most important.

1. The CFM of a supercharger is VITAL in the amount of power it will create, as is the size of the impeller.
2. The max psi of a supercharge has nothing to do w/ the amount of PSI it will create at any impeller speed.
3. The amount of boost a supercharger makes is dependant on about 10 billion things. How well the engine moves air, temperature, outside pressure (which can vary), the engine it is attached to etc.
4. Although air coming out of the supercharger may be slightly pressurized, it will still need time to build up boost even once the impeller gets up to speed (ie if you get the impeller pumping enough to make 12 psi in your specific application, it will take it some time, however small that time may be, to build up 12psi.) And the more free flowing your engine is, the longer it will take your supercharger to build up that boost.

You have told me you are quoting all this stuff from a book. Well, either you are misunderstanding/misapplying the book, or I disagree with the book [img]smile.gif[/img] I find too many inconsistancies in your arguement to accept it.

Like you say that the "ever decreasing" (which really isn't) pipe in your supercharger compresses air, then you say the container doesn't effect compression. So the container does, now it doesn't?

You will need much better proof than "It just is" to convince me...

[ July 07, 2002: Message edited by: strobhen ]</p>

[daWhoady]

Ok, some external compression superchargers just dump air and the compression occurs in the intake manifold, but in a centrifugal supercharger, the compression occurs in the compressor itself.

<blockquote>quote:</font><hr> Originally posted by strobhen:
Air is sucked into the middle of the fan, and is then slung to the outer housing, and then forced out the opening, that snail type opening is common to all centrifugal fans, and in itself provides absolutely no compression (assuming the opening is big enough to let out the air the fan pumps in). <hr></blockquote>

<blockquote>quote:</font><hr> First off, the cross sectional path in that snail housing is ever-increasing. That supercharger spins counterclockwise. Air is slung to the outside of the housing, spun counterclockwise until forced out of the opening.<hr></blockquote>

The snail-like housing was designed specifically to compress the air. The compression side is ever increasing up to the outlet. It was designed that way to act as a diffuser. The air is brought in through the inlet hole and is accelerated by centrifugal force. With the increasing housing, the air is then slowed down. The compression takes place through diffusion, where the diffuser acts as a nozzle in reverse to slow down the air without turbulance. Slowing down the air causes it to increase in pressure and in temperature.

[ July 09, 2002: Message edited by: daWhoady ]</p>

[Dojo2000]

Hey :mad: this argument was never finished [img]tongue.gif[/img]

TTT

I'd like to find out who's right. [img]graemlins/dunce.gif[/img]

[daWhoady]

Wow......grave digger

<blockquote>quote:</font><hr> Originally posted by Dojo2000:
I'd like to find out who's right. [img]graemlins/dunce.gif[/img]
<hr></blockquote>

Let's just say me, it would make everything much easier.....right? hello....right?!? :D